The blood-brain barrier (BBB) is responsible for the homeostasis between the cerebral vasculature and the brain and it has a key role in regulating the influx and efflux of substances, in healthy and diseased states. Stem cell technology offers the opportunity to use human brain-specific cells to establish in vitro BBB models. Here, we describe the establishment of a human BBB model in a two-dimensional monolayer culture, derived from human induced pluripotent stem cells (hiPSCs). This model was characterized by a transendothelial electrical resistance (TEER) higher than 2000 Ω∙cm2 and associated with negligible paracellular transport. The hiPSC-derived BBB model maintained the functionality of major endothelial transporter proteins and receptors. Some proprietary molecules from our central nervous system (CNS) programs were evaluated revealing comparable permeability in the human model and in the model from primary porcine brain endothelial cells (PBECs).
Huntington’s
disease (HD) is a neurodegenerative disease
caused by polyglutamine expansion in the huntingtin protein. For drug
candidates targeting HD, the ability to cross the blood–brain
barrier (BBB) and reach the site of action in the central nervous
system (CNS) is crucial for achieving pharmacological activity. To
assess the permeability of selected compounds across the BBB, we utilized
a two-dimensional model composed of primary porcine brain endothelial
cells and rat astrocytes. Our objective was to use this in vitro model
to rank and prioritize compounds for in vivo pharmacokinetic and brain
penetration studies. The model was first characterized using a set
of validation markers chosen based on their functional importance
at the BBB. It was shown to fulfill the major BBB characteristics,
including functional tight junctions, high transendothelial electrical
resistance, expression, and activity of influx and efflux transporters.
The in vitro permeability of 54 structurally diverse known compounds
was determined and shown to have a good correlation with the in situ
brain perfusion data in rodents. We used this model to investigate
the BBB permeability of a series of new HD compounds from different
chemical classes, and we found a good correlation with in vivo brain
permeation, demonstrating the usefulness of the in vitro model for
optimizing CNS drug properties and for guiding the selection of lead
compounds in a drug discovery setting.
While blood–brain barrier (BBB) dysfunction has been described in neurological disorders, including Huntington’s disease (HD), it is not known if endothelial cells themselves are functionally compromised when promoting BBB dysfunction. Furthermore, the underlying mechanisms of BBB dysfunction remain elusive given the limitations with mouse models and post mortem tissue to identify primary deficits. We established models of BBB and undertook a transcriptome and functional analysis of human induced pluripotent stem cell (iPSC)-derived brain-like microvascular endothelial cells (iBMEC) from HD patients or unaffected controls. We demonstrated that HD-iBMECs have abnormalities in barrier properties, as well as in specific BBB functions such as receptor-mediated transcytosis.
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